Research On Parallel Vectored Thruster And Maneuverability Of Underwater Vehicle

As a new underwater propulsion technology,vectored thrust can improve the flexibility and agility of underwater vehicle,has important significance for the exploration of marine resources.The aim of this paper is to overcome disadvantages of multi-propeller and rudder,such as complexity of control,unstability at low speed.A new vectored thruster,which combines guiding device and propulsion system,is designed to realize propulsion mode of single manipulator and multidimensional attitude,and consequently improve the maneuverability of underwater vehicle.A novel vector-thrust mechanism is designed by structure synthesis of spherical parallel manipulator.The feasibility and reasonability of mechanism scheme is demonstrated by analysis of kinematic performance in theory.Kinematics and dynamic models of vectored thrust underwater vehicle are established for motionprediction and maneuverability evaluation.Then viscous flow filed of underwater vehicle and hydrodynamic performances of vectored thruster are analyzed using computational fluid dynamics method.Eventually the prototype of underwater vehicle is developed;tank tests and lake experiments are conducted to verify the maneuverability of vectored thrust underwater vehicle.Results and conclusions of the study are summed up as follows(1)A new spherical parallel manipulator 2-RPC&2-RPCRU is proposed.Two rotational degrees of freedom are calculated based on screw theory;the forward and inverse solution of position and velocity are worked out through coordinate transformation and space analytic geometry method;the Jacobian matrix is obtained by kinematic influence coefficient The mechanism is proved to have specific kinematic characteristic,decoupling property and no singularity behavior.(2)Propulsion mode of multi-attitude with single manipulator is proposed for underwater vehicle without fin and rudder.Kinematic model with six degrees of freedom is set up,and numerical simulations are given to testify the multi-attitude of the vectored thrust underwater vehicle,such as pitch and yaw.Considering hydrodynamic coefficients of hull without fin and rudder,introducing concept of scaling factor,the nonlinear dynamic model is built.Using Runge-Kutta algorithm,the dynamic model is solved to testify the flexibility of movement in vectored thrust.(3)Perturbation models for longitudinal and transverse motion of vectored thrust underwater vehicle are established,and stability margin index is proposed for evaluating the maneuverability.The stability margin of longitudinal and transverse motion are worked out to be 0.7036 and 0.7798,respectively,which guarantees the dynamic stability of underwater vehicle;the perturbation models are analyzed,transition curves of a series of motion parameters shows the convergence and quick response.(4)The complete flow field computation method of vectored thrust underwater vehicle is proposed.On the base of computational fluid dynamics method,the viscous flow field models of underwater vehicle at diverse vectored thrust angles are built using RANS equations and SST k-? turbulence model.Computation results show that the propeller generates more thrust at large vectored angle,and meanwhile need more torque;the pressure distribution on the blades and chord wise differential pressure show asymmetry at large vectored angle;pressure before propeller disk tend to decrease and thrust deduction fraction tends to increase with the increase of vectored thrust angle.(5)Prototype of vectored thrust underwater vehicle is developed independently.Unit module and complete machine of the underwater vehicle are tested,then tank tests and lake experiments are carried out.Directional stability is reflected by forward sailing test;turning performance is testified through rotational motion experiment in horizontal plane;and steering quality is verified by the zigzag motion test.The experimental results validate the correctness of theoretical calculation,and demonstrate better maneuverability of the vectored thrust underwater vehicle.